Induced dipole dominant giant electrorheological fluid

Traditional dielectric electrorheological fluid(ER)is based on the interaction of dielectric particle polarization,and the yield stress is low,which cannot meet the application requirements.The giant ER(GER)effect is caused by orientations and interactions of polar molecules adsorbed on the particle surfaces.Despite the high yield stress,these polar molecules are prone to wear and fall off,resulting in a continuous reduction in shear stress of GER liquid,which is also not suitable for application.Here we introduce a new type of ER fluid called induced dipole dominant ER fluid(ID-ER),of which the particles contain oxygen vacancies or conductor microclusters both prepared by high energy ball milling(HEBM)technique.In the electric field E,oxygen vacancies or conductor microclusters form induced dipoles.Because the local electric field E_(loc) in the gaps between particles can be two to three orders of magnitude larger than E,the induced dipole moments must be large.The strong interactions of these induced dipoles make the yield stress of the ID-ER fluid reaching more than 100 kPa.Since there are oxygen vacancies or conductor microclusters everywhere in the particles,the particles will not lose the function due to surface wear during use.The experimental results show that the ID-ER fluid possesses the advantages of high shear stress,low current density,short response time,good temperature stability,long service life,and anti-settlement,etc.The comprehensive performance is much better than the existing ER materials,and also the preparation method is simple and easy to repeat,thus it should be a new generation of ER fluid suitable for practical applications.

New Dispersed Phase of Electrorheological Fluids:TiO_2 Coating Graphite Particles

We have prepared novel coated particles, with a conductor graphite core and a dielectric TiO2 coating, as the dispersed phase of electrorheological fluids. One order of magnitude enhancement in the shear stress is obtained by using such composite particles, when it is compared with that of TiO2 particles. The experimental results show a way to get excellent ER system.

Effect of Carrier Liquid on Electrorheological Performance and Stability of Oxalate Group-modified TiO2 Suspensions

By using oxalate group-modified TiO2 nanoparticles as the dispersing phase, different kinds of silicone oil with various viscosities and terminal groups（hydroxyl, hydrogen, and methyl） were used as the dispersing media to prepare different electrorheological（ER） fluids. Their zero-field viscosity, yield stress under direct current electric fields, ER efficiency, shear stability, leakage current density, and sedimentation stability were tested to study the effect of carrier liquid on the properties of ER fluids. The results indicate that the zerofield viscosity, the yield stress, and the leakage current density increase with increasing viscosity of the silicone oils. The effects of the viscosity on the ER efficiency, the shear stability, and the sedimentation ratio depend on the competition between the viscous resistance and the aggregation of the particles. Among the three ER fluids prepared with silicone oil with different terminal groups, hydroxyl-terminated oil based sample has the highest zero-field viscosity, the highest field-induced yield stress and ER efficiency, the largest current density, and the best sedimentation stability.

PERCOLATION TRANSITION IN ELECTRORHEOLOGICAL FLUIDS

The electric conductivity, dynamic modulus and yield stress of the developed electrorheolo-gical fluid (ERF) are measured at different volume fraction and different electric field strengthusing a modified Rheometrics Mechanical Spectrometer (Model 605). The percolation theory isintroduced to explain electrorheological effect and found that the ERF′s have the similarpercolated network structure as that of other ordinary suspensions with a critical volume fractionvalue independent of electric field strength. A master curve of dimensionless modulus againstdimensionless volume fraction is obtained. which shows that the essence of ER phenomenonactually is one kind of the second ofder phase transition.

Electrorheological Fluids Based on Titania Particles Coated with Silica and Their Application in Smart Windows

The electrorheological (ER) fluids are colloidal suspension of highly polarizable particles in a non-conducting solvent. Chains of submicron-sized particles formed along an applied DC electric field by the so-called electrorheological effect. According to the obvious change of transmittance of the ER fluids in a DC electric field when the polarized particles arranged along the field, the model of smart window was proposed by sandwiching the ER fluids based on titania particles coated with silica between a pair of In-Sn oxide (ITO) coated glasses. The solar transmittance change as much as 48.0% was obtained with the wavelength of 500 nm at the maximum on applying and removing the electric field of 500 V/mm.

A New Modified Conductivity Model for Prediction of Shear Yield Stress of Electrorheological Fluids Based on Face-center Square Structure

A new modified conductivity model was established to predict the shear yield stress of electrorheological fluids (ERF). By using a cell equivalent method, the present model can deal with the face-center square structure of ERF. Combining the scheme of the classical conductivity model for the single-chain structure, a new formula for the prediction of the shear yield stress of ERF was set up. The influences of the separation distance of the particles, the volume fraction of the particles and the applied electric field on the shear yield stress were investigated.

Smart Property of Homogeneous Electrorheological Fluid and Its Application in Reducing Seismic Responses of Engineering Structures

The smart properties of homogeneous electrorheological fluid (HERF) containing side-chain type liquid crystalline polymer were studied and an actual HERF damper with an adjustable viscosity was produced.A mechanical model of the HERF smart damper was established on the basis of experiment and theoretical analysis.Then a controlled equation of SDOF structure by HERF damper was derived and a semi active control strategy based on optimal sliding displacement of damper was presented.The simulation results for a single story frame structure indicate that HERF,which may avoid some defects of common particles suspended ER fluids,is an excellent smart material with better stability.Using the semi active control strategy presented,HERF smart damper controlled could effectively reduce seismic responses of structures and keeps the control stable at all times.

The electric field and frequency responses of giant electrorheological fluids

The giant electrorheological （ER） fluid is based on the principle of a polar molecule dominated electrorheological （PM-ER） effect. The response of the shear stress for PM-ER fluid in alternate electric fields with triangle/square wave forms for different frequencies has been studied. The results show that the shear stress cannot well follow the rapid change of electric field and the average shear stresses of PM-ER fluids decrease with the increasing frequency of the applied field due to the response decay of the shear stress on applied field. The behavior is quite different from that of traditional ER fluids. However, the average shear stress of PM-ER fluid in a square wave electric field of iE at low frequency can keep at high value. The obtained knowledge must be helpful for the design and operation of PM-ER fluids in the applications.

RESEARCH ON BEHAVIORS OF ELECTRORHEOLOGICAL FLUID-BASED SEMIACTIVE ROBOT FINGERTIPS

A new design of robot gripper with electrorheological fluid (ERF) semiactive tips is described. There are two remarkable properties using this fingertip. One is the higher lifting capability at little grasp force, which can realize stable grasp. Another is the damping controllable which can be used for controlling contact forces. A viscoelastic plastic model for normal direction of the fingertip is proposed to explore the contact behavior. The electric field strength is induced into the dynamic model of contact transition for simulations. The simulation results and conclusions are given.

Polar molecule dominated electrorheological effect

The yield stress of our newly developed electrorheological （ER） fluids consisting of dielectric nano-particles suspended in silicone oil reaches hundreds of kPa, which is orders of magnitude higher than that of conventional ones. We found that the polar molecules adsorbed on the particles play a decisive role in such new ER fluids. To explain this polar molecule dominated ER （PM-ER） effect a model is proposed based on the interaction of polar molecule-charge between the particles, where the local electric field is significantly enhanced and results in the polar molecules aligning in the direction of the electric field. The model can well explain the giant ER effect and a near-linear dependence of the yield stress on the electric field. The main effective factors for achieving high-performance PM-ER fluids are discussed. The PM-ER fluids with the yield stress higher than one MPa can be expected.

Effect of surfactant on the dielectric and electrorheological properties of zinc borate/silicone oil dispersions

Zinc borate(ZB)particles dispersed in silicone oil(SO)at concentrations of φ=5vol%-20vol% were subjected to dielectric analysis to elucidate their polarization strength,time,and mechanism.Results revealed that all virgin dispersions lacked polarization.Triton X-100,a non-ionic surfactant,was added to ZB/SO dispersions to enhance the polarizability of ZB particles.The addition of 1vol% Triton X-100 enhanced the polarizability of ZB/SO dispersions,and the 15vol% ZB/SO system provided the highest dielectric difference Δε′(the difference in ε′values at zero and infinite frequency,Δε′=ε0–ε∝)of 3.64.The electrorheological(ER)activities of the ZB/SO/Triton-X dispersion system were determined through the ER response test,and viscoelastic behaviors were investigated via oscillation tests.A recoverable deformation of 36% under an applied electrical field strength of 1.5 kV/mm was detected through creep and creep recovery tests.

Sol-Gel Preparation of Graphite/TiO_2 Composite Particles and Their Electrorheological Effect

Graphite/TiO2 composite particles were obtained by sol-gel technique in this paper. The structure and characteristic of the composite particles are analyzed by XRD, SEM and TG-DTA. The electrorheological properties of the ER fluid containing the particles were measured by a Couette-type rheometer under shear rates of 1-136 s-1 and AC electric fields of 0-3 kV/mm. The experimental results show that the leaking current density of the ER fluid is higher than that of pure titanium dioxide particles dispersed in damping oil. The shear yield stress of the ER fluid increases with increasing electric field and exhibits a typical Bingham flow behavior. The suspension demonstrates an excellent ER performance (τ/τo=1200) compared with conventional ER fluids (τ/τ0 ≤500). The sedimentation of the ER fluid is improved obviously due to the coating effect of the particles.

ELECTRORHEOLOGICAL PROPERTIES OF DIATOMITE/SILICONE OIL SUSPENSIONS UNDER DC FIELDS

In this study, electrorheological （ER） behavior of suspensions prepared from 3.0 and 9.0 μm diatomite particulate, dispersed in insulating silicone oil （SO） medium was investigated. Sedimentation stabilities of suspensions （c = 5 wt%） prepared using these diatomite powders were determined to be 32 days （d = 3 μm） and 24 days （d = 9 μm）, respectively. ER activity of all the suspensions was observed to increase with increasing electric field strength, concentration and decreasing shear rate. Shear stress of diatomite suspensions increased linearly with increasing concentrations of the particles and with the applied electric field strength. Electric field viscosity of all the suspensions decreased sharply with increasing shear rate and particle size, showing a typical shear thinning non-Newtonian visco-elastic behavior. Effects of high temperature and polar promoter onto ER activity ofdiatomite/SO system were also investigated.

ELECTRORHEOLOGICAL PROPERTIES OF TALC POWDER/SILICONE OIL SUSPENSIONS UNDER DC FIELDS

In this study, the electrorheological （ER） behavior of suspensions prepared from d50 = 2.4 lam talc powder, dispersed in insulating silicone oil （SO） medium was investigated. Sedimentation stabilities of suspensions （c = 5 wt%） prepared using these talc powder powders were determined to be 78 days. The ER activity of all the suspensions was observed to increase with increasing electric field strength, concentration and decreasing shear rate. The shear stress of talc powder suspensions increased linearly with increasing concentrations of the particles and with the applied electric field strength. Electric field viscosity of all the suspensions decreased sharply with increasing shear rate and showed a typical shear thinning non-Newtonian visco-elastic behavior. Effects of frequency on the ER activity of talc powder/SO system were also investigated.

Facile Synthesis of Polypyrrole/Titanate Core-Shell Nanorods and Their Electrorheological Characteristics

In this work, polypyrrole (PPy)/titanate (TN) composite nanorods were successfully synthesized using cetyl trimethyl-ammonium bromide (CTAB) as a structure-directing agent by in situ chemical oxidative polymerization. The structural characterization indicated that the new composite rods were core (TN)-shell (PPy) nanostructure with the average diameter in the range of 250-300 nm. Further, this semiconducting composite can be used as a dispersed phase in silicone oil for a new electrorheological (ER) fluid, and its ER behavior was investigated under steady and oscillatory shear. It was found that the PPy/TN fluid showed typical ER characteristics under an external electric field.

电流变液(ERF)换向阀的设计

研究了电流变液换向阀的设计原理，设计方法一并对该换向阀的性能进行了分析。

ERF减振器的模糊控制技术

电流变流体 (Electrorheological fluid简称 ERF)是一种新型的智能材料 ,将其作为减振器的阻尼介质 ,运用模糊逻辑控制技术实现了变阻尼的非线性控制 ,并通过对其控制效果进行仿真试验 ,与常规的被动控制和 PID控制仿真效果相比较 ,证实了该方案的优越性。

ERF减振器的模糊控制系统设计

电流变流体是一种新型的智能材料,在本文中,将其作为减振器的阻尼介质,设计了一种新型的ERF减振器,并针对这种ERF减振器,设计了相应的模糊控制算法,最后用MCS-51单片机和协处理器F200模糊控制芯片构成了单片机模糊控制减振系统。

ERF减振器的模糊控制系统设计

电流变流体是一种新型的智能材料,在本论文中,将其作为减振器的阻尼介质,设计了一种新型的ERF减振器,并针对这种ERF减振器,设计了相应的模糊控制算法,最后用MCS-51单片机和协处理器F200模糊控制芯片构成了单片机模糊控制减振系统。

基于模糊控制的ERF减振器设计

电流变流体是一种新型的智能材料,在本论文中,将其作为减振器的阻尼介质,设计了一种新型的ERF减振器,并针对这种ERF减振器,设计了相应的模糊控制算法,同时通过对其控制效果进行仿真试验,证实了该算法的可行性。